Abstract: On January 19, 2001, MSHA published a final rule addressing diesel
particulate matter (DPM) exposure of underground metal and nonmetal
miners (66 FR 5706). The final rule established new health standards
for underground metal and nonmetal mines that use equipment powered by
diesel engines. The rule established an interim concentration limit of
400 micrograms of total carbon per cubic meter of air that became
applicable July 20, 2002, and a final concentration limit of 160
micrograms to become applicable after January 19, 2006. Industry
challenged the rule and organized labor intervened in the litigation.
Settlement negotiations with the litigants have resulted in further
regulatory actions on several requirements of the rule. One final rule
was published on February 27, 2002 (67 FR 9180). MSHA issued an advance
notice of proposed rulemaking (ANPRM) on September 25, 2002 (67 FR
60199) to obtain additional information and published a notice of
proposed rulemaking (NPRM) in August 2003 (68 FR 48668). MSHA issued a
final rule on June 6, 2005 (70 FR 32868) that revises MSHA's existing
standards addressing diesel particulate matter (DPM) exposure in
underground metal and nonmetal (M/NM) mines. The rule, among other
things, changes the interim concentration limit measured by total
carbon (TC) to a comparable permissible exposure limit (PEL) measured
by elemental carbon (EC). MSHA is developing a rule to phase in
implementation of the final limit.

Statement of Need: As a result of the first partial settlement with the litigants, MSHA
published two documents in the Federal Register on July 5, 2001. One
document delayed the effective date of 57.5066(b) regarding the tagging
provisions of the maintenance standard; clarified the effective dates
of certain provisions of the final rule; and gave correction amendments
(66 FR 35518).

The second document was a proposed rule to clarify 57.5066(b)(1) and
(b)(2) of the maintenance standards and to add a new paragraph (b)(3)
to 57.5067 regarding the transfer of existing diesel equipment from one
underground mine to another underground mine (66 FR 35521). The final
rule on these issues was published February 27, 2002, and became
effective March 29, 2002.

As a result of the second partial settlement agreement, MSHA proposed
specific changes to the 2001 DPM final rule. On September 25, 2002,
MSHA published an ANPRM. In response to commenters, MSHA proposed and
finalized changes only to the interim DPM standard of 400 micrograms
per cubic meter of air. MSHA also committed to proposing a rule to
revise the final DPM limit of 160 micrograms per cubic meter of air.

Summary of Legal Basis: Promulgation of this regulation is authorized by sections 101 and 103
of the Federal Mine Safety and Health Act of 1977.

Alternatives: This rulemaking would amend and improve health protection from that
afforded by the existing standard.

Anticipated Cost and Benefits: MSHA's preliminary economic analysis indicates that making the changes under consideration would result in a net cost savings to the mining
industry.

Risks: A number of epidemiological studies have found that exposure to diesel
exhaust presents potential health risks to miners. These potential
adverse health effects range from headaches and nausea to respiratory
disease and cancer. In the confined space of the underground mining
environment, occupational exposure to diesel exhaust may present a
greater hazard due to ventilation limitations and the presence of other
airborne contaminants, such as toxic mine dusts or mine gases. We
believe that the health evidence forms a reasonable basis for reducing
miners' exposure to diesel particulate matter. Proceeding with
rulemaking on the provisions discussed above will more effectively
reduce miners' exposure to DPM.